Adjustable presser devices for sewing machines



March 18, 1969 JIN TAKAHASHI 3,433, 3

ADJUSTABLE PRESSER DEVICES FOR SEWING MACHINES Filed June 13, 1967 I NVEN TOR.

Jin Tokahoshi United States Patent Olfice 3,433,193 Patented Mar. 18, 1969 3 Claims ABSTRACT OF THE DISCLOSURE A flat element of a slidable linkage having a horizontal elongated aperture is mounted on a mounting bracket with the flat element connected to a rod element having a spring between it and a presser bar. A regulating member having a crank pin is mounted on the mounting bracket with the crank pin in the horizontal elongated aperture in the flat element for shifting the slidable linkage and hence changing the pressure on the presser bar.

BACKGROUND OF THE INVENTION Field 0] the invention This invention relates to sewing machines having a work presser device for yieldingly urging the work fabric against the work support and in opposition to the work feeding mechanism at the stitching point. More particularly, this invention relates to a novel and improved means for effecting adjustments of pressure to be exerted by the presser device and for maintaining an adjusted pressure.

DESCRIPTION OF THE PRIOR ART In prior presser devices, pressure regulation has been accomplished either by an adjustable knurled knob at the top of the presser bar or by a more complicated mechanism actuated by a knob on the side of the sewing head. In the presser devices in which the pressure is adjusted by a knob at the top of the presser bar, unequal increments of pressure are introduced because of the build-up of pressure in the coil spring between the knob and the presser bar. In addition the knob is hard to turn when the coil spring is under compression because the coil spring tends to lock the threads of the knob against the threads on which the knob turns. In the more complicated mechanisms, binding and cocking of parts created by inherent angular forces are frequent.

SUMMARY OF THE INVENTION It is therefore an object of this invention to provide a novel and improved spring pressure regulating and indicating mechanism having a combination of parts moving substantially parallel to each other and free from the binding and cocking of parts created by angular forces.

It is a further object of this invention to provide a pressure regulating means which requires the expenditure of less effort by the operator when making adjustments and especially so at the higher pressure positions. Most regulators have a build-up of pressure, which frequently causes a locking of the moving parts. This invention is so constructed as to eliminate this undesirable locking effect.

It is still a further object to provide a pressure regulating means which is inexpensive to manufacture and in which excessive wear and tear on the working parts is eliminated,

Having in mind the above and other objects that will be evident from an understanding of this disclosure, the invention comprises the devices, combinations and arrangements of parts as illustrated in the presently preferred embodiment of the invention which is hereinafter set forth in such detail as to enable those skilled in the art readily to understand the functions, operation, construction and advantages of it when read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 represents an end elevational view of the sewing head portion of a sewing machine casing with certain parts broken away better to illustrate the mechanism carried within the sewing head.

FIG. 2 is an enlarged cross-sectional view taken substantially along line 22 of FIG. 1.

FIG. 3 is an enlarged cross-sectional view taken substantially along line 33 of FIG. 1.

FIG. 4 is a disassembled perspective view of the supporting bracket for the pressure regulating member together with the shiftable spring compressing rod and its adjusting driving and holding members.

DESCRIPTION OF THE PREFERRED EMBODIMENT The presser mechanism as herein illustrated is of the type described in US, Patent No. 3,055,326, granted Sept. 25, 1962 to R. G. Greulich and is embodied in a sewing machine 10 having a work supporting surface 11 and an overhanging sewing head casing 12. The presser mech anism comprises a presser bar 13 slidably mounted in a sleeve or bushing 14 mounted in the head casing 12. The lower end of the presser bar 13 has secured to it a workengaging presser foot 15.

The presser bar 13 is provided with an axial bore 16 extending longitudinally thereof from the upper end. down to an abutment 17. Disposed within the bore 16 is a compression spring 18 bearing against the abutment 17 at its lower end and at its upper extremity engaging the lower end 19 of the rod portion 20a of the twopiece linkage member 20. To assure the alignment of the rod portion 20a and the presser bar 13 when the coil spring 18 is relaxed, the rod 20a is extended forming a reduced portion 21 longitudinally down through the coil spring 18 and guided within a supporting bore 22 in the presser bar 13.

At the upper extremity of the presser bar 13 is secured a presser lifting and guiding collar 23 to cooperate with a presser lifting lever 24 fulcrumed on the sewing head casing 12. This enables the operator to raise and lower the presser bar without effecting any change in the setting of the pressure regulating mechanism indicated generally at 30.

Secured inside the sewing head casing 12 by fastening screws 3131 is mounted a pressure regulating supporting bracket indicated generally at 32. The fastening screws 3131 pass through the sewing head casing 12 into threaded holes 33-33 of a portion 34 extending perpendicularly from a front body portion 35 of the supporting bracket 32. The front body portion 35 is so arranged as to extend in a plane substantially parallel to the axis of the presser bar 13. Mounted centrally in a threaded hole 36 of the front body portion 35 is a shouldered pivot stud 37 which is locked against rotation by a lock nut 38. Journaled about the pivot stud 37 is a pressure regulating member indicated generally at 39. A flat portion 20b of the two-piece linkage member 20 is formed with a longitudinally elongated guiding aperture 41 embracing the pivot stud 37 and is guided for travelling substantially parallel to the axis of the presser bar 13 by two guiding lugs 4242 which embrace a rectangular car 43 extending downwardly from the front body portion 35 of the pressure regulating supporting bracket 32, as best shown in FIGS. 3 and 4. Located between the two guiding lugs 42-42 of the flat portion 20a is an aperture 44 for receiving the offset and outturned portion 45 of the shiftable rod 20a. The outturned portion 45 is guided by an elongated aperture 46 formed on the rectangular car 43 so as to move in a path substantially parallel to the axis of the presser bar 13. The linkage member 20 could be fabricated as one rigid member 'but this would necessitate closer tolerances to the moving parts.

Extending out from the back surface of the pressure regulating member 39 is a crank pin 47 which extends into an elongated aperture 48 in the fiat portion 20b. The elongated aperture 48 is disposed perpendicular to the guiding aperture 41, and defines planar crank pin engaging surfaces on the fiat portion 20b which extends perpendicular to the axis of the pressurebar 13. Partial rotation of the regulating member 39 Will rotate the crank pin 47 imparting a raising or lowering force to the twopiece linkage member 20, in turn, compressing or releasing the coil spring 18, therefore, increasing or decreasing the pressure on the work fabric.

To keep the pressure regulating member 39 in any selected one of a plurality of setting positions corresponding to a range of pressure, a plurality of detents 49 are located in equally spaced relation along a common radius about the pivot stud 37 as best shown in FIGS. 3 and 4. To cooperate with the detents 49 is a detent pin 50 constrained in a hole 51 formed in the pressure regulating member 39. A detent pin coil spring 52 is so designed as to withstand the counter-rotation pressure created by the presser bar biasing coil spring 18 when the pressure regulator is set at the maximum setting. When reducing the setting, the counter-rotation pressure aids the operator to initiate motion to the regulator especially at the maximum setting. The pressure regulating member 39 is provided with indicia 53 (FIG. 1) corresponding to the number of detents 49. An indicator mark 54 is formed in an arm 55 extending from the front body portion 35 of the sup porting bracket 32, thus indicating to the operator the compression of the coil spring 18 and the amount of pressure with which it is urging the presser bar 13 into engagement with the Work supporting surface 11.

Having thus set forth the nature of this invention, what I claim herein is:

1. A presser bar pressure regulating device for a sewing machine having a casing, a presser 'bar, means on said casing supporting said presser bar for axial sliding movement, a slidable linkage suppolted relatively to said casing for movement in a direction axially of said presser bar, spring means acting between said linkage and said presser bar, said linkage being formed with a planar actuating surface extending perpendicularly to the said direction of sliding movement thereof, an operator influenced regulating member shiftably supported on said casing for movement in a direction axially of said presser bar and operatively engaging said planar actuating surface of said slidable linkage, a pressure regulating support bracket mounted on said casing, means on said support bracket for constraining said slidable linkage to move in a direction axially of said presser bar, said slidable linkage including a flat element guided by said support bracket for movement in a direction axially of said presser bar and shiftable by said regulating member, a rod element guided by said presser bar for movement in a direction axially of said presser bar and interconnected with said flat element, said regulating member including a knob, a coaxial pivot stud, a detent pin and a crank pin engaging said planar actuating surface, said flat element of said slidable linkage including an elongated clearance aperture for said pivot stud oriented substantially parallel to the axis of the presser bar, said support bracket including means for connecting said pivot stud to said mounting bracket and a series of detents arranged in an arc to mate with said detent pin.

2. A presser bar pressure regulating device for regulating the pressure which a presser bar spring applies to an endwise slidable presser bar of a sewing machine, said presser bar pressure regulating device, adapted for mounting on the sewing machine, comprising means for adjusting the amount of pressure applied by the spring to said presser bar including a movable abutment member, a bracket adapted to be secured to the sewing machine, a unitary actuating link mounted for sliding movement on said bracket, means for guiding said unitary link in a direction parallel to the direction of endwise move ment of the presser bar, means for operatively connecting said movable abutment member to said unitary link, said unitary link having a slot formed therein, said slot being formed substantially transversely of the path of endwise movement of said presser bar, means for moving said unitary link in a direction parallel to the direction of endwise movement of the presser bar when said presser bar pressure regulating means is mounted on the sewing machine, said last named means including a rotatable knob and a finger secured to said knob radially of the axis about which said knob is rotated, said finger being received by said slot in sliding engagement therewith so that as said knob is rotated said finger moves said unitary link in a direction parallel to the direction of endwise movement of the presser bar thereby to move said abutment member and adjust the pressure applied to the presser bar by said spring.

3. A presser bar regulating device as set forth in claim 2 wherein said bracket has formed therein a plurality of detent recesses arranged in an arc and a spring biased detent pin is connected to said knob and positioned selectively to engage said detent recesses as said knob is rotated.

References Cited UNITED STATES PATENTS 2,554,970 5/1955 Adler 112-235 3,055,326 9/1962 Grevlich 112-235 3,303,804 2/1967 Lesort Q. 112-235 PATRICK D. LAWSON, Primm'y Examiner. 

